The present invention relates to calls and transactions in a communications network, such as an Signaling System Seven (SS7) network, and, more particularly, to monitoring transactions in an SS7 network to detect when a mass call condition exists for a particular destination telephone number.
Common channel signaling networks, such as the Signaling System Seven (SS7) based signal system, use dedicated channels to pass digital messages between systems for call setup, call control, call routing, and other functions. These dedicated signaling channels are part of a network that is separate from the network that carries the actual voice and data signals. An SS7 network is a separate switching system which is used prior to, during, and at the end of an actual voice or data call. The SS7 network is used to route control information. Whenever two switches or elements have to pass call control information during or prior to a phone call, they pass this data via the SS7 signaling network.
There are three basic types of network node elements in an SS7 network. One of them is the Service Switching Point (SSP), which may be a central office switch, a tandem switch or an end office switch. A second principal node element is the Service Control Point (SCP). An SCP acts as a database query server for the rest of the network. An SCP is used in such applications as translating ported telephone numbers, routing 800 calls, tracking roamers in a cellular network, and Alternate Billing Service/Line Identification Database services (or ABS/LIDB) which provide operator-type services. The third principal node element is the Signal Transfer point (STP). An STP is essentially a packet switch that routes the messages from SSPs and SCPs to SSPs and SCPs.
It is possible to combine these three different types of nodes into a single node. However, in North America, they are typically not combined. An SSP performs only switch functions, an SCP only control functions, and an STP only signal transfer functions. In European telecommunications systems, all of these different functions may be combined into one node.
The SS7 network carries a great deal of information and is extremely critical to the operation of the phone system. If an SS7 network is not functioning, or if portions of it are not operating, the phone system simply cannot deliver phone calls, even though all of the voice circuits are operating properly. The capacity and complexity of the SS7 network is small in terms of circuitry and bandwidth utilized by an end user compared to previous voice and data networks. The circuitry of the SS7 network is therefore much more critical. The actual elements in the SS7 network do not provide all the information required in network operations to manage and to determine the health and state of an SS7 network. It is therefore necessary for the telephone industry to deploy surveillance equipment to monitor the links connecting the nodes of the SS7 network.
The topology of the network is such that STPs are typically deployed in a mated pair configuration at geographically separate locations. Connected to a mated pair of STPs will be a set of SSPs and SCPs. This conglomeration of SSPs, SCPs and mated Pair STPs is called a cluster. Clusters are then connected by D-Quad links between STP mated pairs.
When any transaction or message is sent between two different devices on the network, it is often the case that the messages going from switch A to switch B travel one route on the network while the messages going from switch B to switch A travel a different route. The network surveillance equipment that monitors the link is designed to capture and correlate as much signaling information as possible regardless of network activity. Because of the different data paths that messages may take, it is difficult to do this correlation above what is called the transport layer when monitoring links at the STP sites. An example of an application level problem would be where a subscriber has a problem getting his/her calls delivered. The telephone company may attempt to fix the problem by doing a trace of all data pertaining to that subscriber""s phone number, but the data may not all be located at one point. The data may be all in one STP, or split in some fashion, partially in one STP and partially in the other STP of a mated pair, which may be in a different city many miles away.
In an SS7 network, each telephone is connected to a single end office, which may be an SSP or some other switch. The end office is connected to the SS7 network through one or more STPs. All calls that are directed to a particular destination telephone must pass through that telephone""s assigned end office. Each end office has the capability to handle a finite number of calls. Under normal conditions, incoming calls and transactions to an end office are spread among a large number of telephones and destination telephone numbers. However, in some situations, a large volume of calls may be directed to a particular destination telephone number. If the incoming call volume exceeds the capabilities of the end office, then the switch will not be able to completed some of the calls and they will be dropped.
If a particular telephone number is used by an unusually high number of callers, then a mass call condition may arise. In a mass call condition the end office is not able to complete all of the incoming calls of the high volume of calls to a particular telephone number. As a result, calls to one telephone detrimentally affect the calls to all telephones connected to the same switch.
It is an object of the present invention to detect when a mass call condition exists and to minimize the effect of the mass call condition on calls to the mass called number and to other telephone numbers.
It is a further object of the present invention to correlate transaction signaling units in an SS7 network into transaction records and to use the transaction records to detect information about highly called telephone numbers that are affected by the mass call condition.
These and other objects, features and technical advantages are achieved by a system and method in which monitoring units non-intrusively capture transaction signaling units or messages from links in a communications network. The transaction signaling units are correlated in transaction processors. All transaction messages that are related to one transaction are combined into a single transaction record. The transaction records are provided to a processor or state machine which monitors the call load for each destination telephone number.
Monitoring systems that continually monitor, in real time, all calls on a signaling network are disclosed in U.S. Pat. No. 5,592,530, entitled TELEPHONE SWITCH DUAL MONITORS; and in application Ser. No. 09/057,940, filed Apr. 4, 1998, entitled SYSTEM AND METHOD FOR MONITORING PERFORMANCE STATISTICS IN A COMMUNICATIONS NETWORK, the disclosure of which is hereby incorporated by reference herein.
Each monitoring unit processes transaction records to detect mass call onset conditions. A continually updated list of recently detected destination telephone numbers is maintained by a processor on the monitoring unit. If the number of calls to a destination telephone number exceeds a short-term threshold, then the detecting monitoring unit instructs other monitoring units to track the destination telephone number. If the number of calls to the destination telephone number then exceeds a long-term threshold, then a mass call alarm is generated.
When a mass call alarm is generated, the user or network service provider receives certain preselected data. The user may receive point codes for the destination that is receiving the mass call event and for the nodes that are originating the calls to the affected telephone number. Also, the system may provide a telephone number, or a range of telephone number digits, such as an area code or an exchange, that is receiving an abnormally high volume of calls. Alarms and information can also be generated for types of failed call release causes, such as dialed number busy.
It is a feature of the present invention to correlate all transaction messages in a communications network into transaction records representing each transaction over the network. The transactions are detected and correlated using an inter-linked group of monitoring devices.
It is an additional feature of the present invention to monitor destination telephone numbers in said transaction records. A list of most recently detected destination telephone numbers is maintained. For example, the list may comprise the destination telephone numbers detected in a selected period, such as numbers called in the last five seconds. The list of recently called telephone numbers also tracks the number of calls to each destination number within the period. The destination number list is filtered to detect if the number of calls to any of the destinations exceeds a first threshold.
It is another feature of the present invention to provide a destination number that exceeds the first threshold to other monitoring units. All of the monitoring units then detect and forward any relevant transaction records that have the same called number to a central or master mass call monitoring unit. If calls to the destination number exceed a second threshold, then a mass call alarm is generated to warn the service provider or user.
It is further feature of the present invention allow users to select various types of data that is to be provided when a mass call alarm is generated. The data comprises information about the called and calling numbers and point codes. Furthermore, the user can select other information to be provided, such as reasons for call failures or types of release causes.
The present invention provides the user with real-time mass call onset detection on a per phone number basis. The mass call application can be distributed across the network at each monitor. The transaction processors described herein allow for a system in which multiple inbound and outbound messages are correlated into a single unified record per transaction.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.